Method of producing waterproof electrical coils

ABSTRACT

A method of waterproofing electrical coils used particularly in electrical machines in which at least the coil ends or arm portions and the contact end outlets of the coil are coated with a spreadable paste before the coil is wrapped with a substantially unimpregnated insulating material. The paste consists substantially of a pure filler and a volatile solvent. The solvent is removed from the paste by a drying treatment after wrapping but before impregnating the coil with a waterproofing material.

United States Patent 1 Schindelmeiser et a1.

[ METHOD OF PRODUCING WATERPROOF ELECTRICAL COILS [75] Inventors: Fritz Schindelmeiser, Lohfelden;

Hans-Jurgen Kaltschmidt, Berlin; Edmar Strauss, Berlin; Siegfried Foth, Berlin, all of Germany [73] Assignee: Licentia Patent-Verwaltungs-G.m.b.H., Frankfurt am Main, Germany [22] Filed: Mar. 15, 1972 [21] Appl. No.: 234,772

[30] Foreign Application Priority Data Mar. 31, 1971 Germany 7113167 [52] US. Cl 156/185, 117/113, 156/192, 156/276, 174/120 C, 310/208 [51] Int. Cl... H0lb 7/02, HOlb 13/08, H0lb 13/10 [58] Field of Search 156/48, 56, 192, 276, 185; 174/120 C, 120 R, 120 SR; 117/113; 310/43,

[56] References Cited UNITED STATES PATENTS 2,821,498 l/l958 Botts 156/276 X Oct. 8, 1974 2,928,964 3/1960 Jones 156/56 3,042,743 7/1962 Jones 156/56 X 3,048,651 8/1962 Howard et a1. 156/48 X 3,079,519 2/1963 Kitson, Jr. et a1. 156/56 X 3,483,413 12/1969 Logan 174/120 R 3,531,751 9/1970 Sargent 156/56 X Primary Examiner-Douglas J. Drummond Assistant ExaminerBasil .1. Lewris Attorney, Agent, or Firm-Spencer & Kaye [57] ABSTRACT 6 Claims, 5 Drawing Figures PATENTEDmn 8 new:

SHEEI HP 2 PATENTEUDCT 8 I974 3. 84QA16 slim 2 or 2 BACKGROUND OF THE INVENTION The present invention relates to a method for making waterproof electrical coils, and particularly for waterproofing the coil ends or arm portions as well as the contact end outlets of electrical coils for use in electrical machines.

The coils used, for example, in electrical machines are first wrapped with a substantially unimpregnated insulating material, are then inserted, except for the coil ends or arm portions as well as the contact end outlets, into notches of a lamination packet of the ma chine, and then waterproofed by waterproofing the insulating material, for example, by saturation with a cast resin.

When manufacturing waterproof coils, particular care must be taken at the coil ends or arm portions and the contact end outlets because of the fact that at these points cavities are known to develop during the application of the electrical insulating material on the electrical conductors comprising the coil. This is so because of the complex configuration of these coils. If

LII

after impregnating and hardening of theinsulating maany case where the electrical coils are already installed in the electrical machines before impregnation, for economical reasons, it is required that the coils'be waterproof right from the start, i.e., after impregnation. This is due to the fact that after impregnation it is extremely difficult, if not impossible, to remove the coil from the machine. The term waterproof is here to be understood in the sense that it is defined, for example by the underwater test according to NEMA standards, specifically, NEMA M 61, Section III, Part 20.48.

. In the production of coils which are installed in electrical machines after impregnation, the waterproofing of the coils is realized in that each coil is impregnated several times. In coils which are already installed in the machines during the impregnating process, however, a further sealing process, for example,'encasing the coils in cast resin or the like, is performed'Such a further process is principally also possible after the impregnation and hardening of the coils. However, this is very complicated and uneconomical because the electrical contact ends and lines have already been established so that the points to be sealed can be reached only under extreme difficulties. Also, the above-mentioned process has the further drawback that it can very rarely be determined in advance and with accuracy just how many impregnations and hardening processes actually are needed for a perfect seal. Thus, time-consuming intermediate tests under water are required. The production sequence is thus complicated and necessitates perfect drying of the coils before a subsequent impregnation is performed, if necessary. Moreover, usually only the accesses to the cavities are sealed, with the poor thermal properties of the cavities themselves remaining, however. i 5

SUMMARY OF THE INVENTION It is, therefore, a general object of the present invention to provide an improvement in the method of the above-mentioned type which assures simple, economical and safe waterproofing of the contact end outlets and the coil ends or arm portions of electrical coils with only one impregnating process.

This and other objects are accomplished according to the present invention by, prior to the application of the insulating material, coating at least the coil ends or arm portions and the contact end outlets of the electrical coils with a thick but still spreadable. paste consisting substantially only of a pure filler and an easily volatile solvent to fill at least all of the cavities formed by the coil, and by removing the solvent from the paste by a drying treatment after the coil has been wrapped with a substantially unimpregnated insulating material but before the insulating material is impregnated with a resinous water-proofing material.

Advantageously the coil treated according to the method of the invention is inserted into the notches of a lamination packet of an electrical machine prior to the removal of the solvent and subsequent impregnation. It should be understood, however, that the method is equally applicable to use with a coil wherein the solvent has been removed before it is inserted into the lamination packet notches.

In an advantageous embodiment of the present invention, the coil ends or arm portions as well as the contact end outlets are wrapped with a band after the coil has been coated with the paste but before the coil has been wrapped with the insulating material.

In a further advantageous embodiment of the present invention, an angular strip of insulating material is inserted into the space between the contact end outlets and the remainder of the coil before the cavities are filled with paste, with the angular strip being first covered with the paste on at least one side thereof.

Thus the method according to the present invention assures the production'of a homogeneous waterproof insulation at the coil ends or arm portions and at the contact end outlets with but a single impregnation process. As a result, intermediate waterproofing tests are eliminated. The method is thus economical particularly since the materials used for the tiller and for the seal are commercially available and inexpensive, and since the quantity of additional filler material required is low compared to the expense of the otherwise required further impregnation. Moreover, the removal of heat from the coil is substantially improved by the bridging of the cavities.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration in perspective of part of the coil ends or arm portions of the coil waterproofed according to the method of the present invention.

FIG. 2 is a schematic cross-sectional view taken along line 2-2 in FIG. 1 through a coil end or arm portion illustrating the paste filled cavities formed by the coil in these areas and outlines of the encasing material according to the method of the present invention.

FIG. 3 is a schematic illustration in perspective of the contact end outlets of a coil waterproofed according to the method of the present invention.

FIG. 4 is a schematic view to an enlarged scale and .in cross section of detail A shown in .FIG. 3 and illustrating the paste filled space between the contact end and the remainder of the coil along with the angular strip within the space and outlines of the encasing ma- -terial according to the method of the present invention.

FIG. 5 is' a schematic cross-sectional view taken along line 5-5 in FIG. 4, illustrating the paste filled space between the contact end and the remainder of the coil and also outlining the encasing material according to the method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularly to the drawings, FIG. 1 shows a coil in which a bundle of conductors 9 is thoroughly and saturatingly covered with a paste 3 before the tape-type insulating material 2 is applied. The paste 3 consists substantially of only a pure filler, e.g., quartz, powdered mica, talcum or the like, which is mixed for processing with an easily volatile solvent into a thick, barely spreadable mass. The solvent can be, e.g., methylene chloride, trichlorethylene, acetone,

alcohol or the like. The applied quantity of paste 3 must be large enough that with the subsequent advantageous encasing in a holding band 8 of an insulating material, all cavities disposed underneath the holding band 8 are entirely filled, see FIG. 2. According to the present invention, the holding band 8 can be, for example, a glass silk band.

The cavities shown inFlG. 2 are formed as a result of, for example, bending ofthe coil. Such bending takes place predominately in the coil end or arm portions, shown in FIG. 1, as well as in the contact end outlets, shown in F IG. 3. Of course it should be understood that the method according to the present invention is applicable to any part of the coil where cavities develop.

In theproduction process the filling of the cavities is best effected in such a manner thatzthe excess paste 3 is squeezed out in advanceby the holding band 8 for each coil to be wound so that a substantially flush relationship is established between the surface of the paste 3 in the cavities and the conductors 9 as shown in FIG. 2. Finally, the still unimpregnated, tape-type insulating material 2 is applied to at least the coil ends or arm portions of the coil. After installation of the thus prepared coil in the notches of a lamination packet of an electrical machine and the removal of the solvent in the paste 3, the impregnation of the material 2 is effected, for example, by saturation in a synthetic resin bath. After a hardening process for the impregnating resin, a waterproof coil end or arm portion insulation is then in existence. Although according to the method described the solvent is removed from the paste 3 after installation of the prepared coil in the notches of the lamination packet, it should be understood that the method also comtemplates the removal of the solvent from the paste 3 before the installation of the prepared coil in the notches of the lamination packet.

The method according to the present invention asapplied to a contact end outlet of a coil will be described with particular reference to FIGS. 3 through 4.

Referring intially to FIG. 3, the contact end outlets 10 are shown in conjunction with a number of defined lengths of the coil, namely, the lengths within the spans L, L,, L, and L The contact end outlets 10 are constructed by partially removing the top conductor of the pack of conductors 9 from the remainder of the conductors and defining thereby a space 10'. The contact end outlets 10 are removed from the remainder of the conductors 9 for a distance L,, while the extent of the space 10' which is filled with paste 3 isdesignated by the length L;,.

The sealing of a contact end outlet begins by slightly lifting the contact end 10 from the remainder of the conductor 9 and winding the contact end 10 with a not yet impregnated insulating tape 1 corresponding to the required number of layers. Then the subsequent coil ends of arm portions are insulated against water over a length L, ina manner described above with respect to the coil shown in FIGS. 1 and 2; however, in this example the coil ends or arm portions are insulated without the use of a holding band 8. Next, the remaining conductors 9 are first wound over a length L, only with one-half of the required layers of the tape-type insulating material 2. Then the space 10 is filled-to excess over the length L;, with the paste 3. For safetys sake, and as an additional barrier, an angular strip or wedge 4 of insulating material which is also saturatedly covered with the paste 3 is first inserted into the space between contact end 10 and the remainder of the conductors 9. The insulated contact ends 10 are now pressed firmly against their respective remaining conductors 9 and a winding head or arm portion of the coil, so that the excess paste 3 is squeezed out of the space 10 over the length L,-,. The squeezed out paste 3 isspread as a result of the pressing force in order to provide a lateral seal.

The coil is then covered with about one-half of the required number of layers of tape-type insulating materials over the langth L The material 5 corresponds to the insulating material 2 used on the contact end 10 over the length L, with the coil end or arm portion. The insulating material 5 is so applied that the length L, is overlapped by the length L;,. Finally the coil is wound with the remaining half of the required layers of the insulating material 6 over the entire length L.

In order to safely fix the contact end 10 and assure a water-proof seal, several turns of a band 7 which shrinks when it becomes hot are wound about the coil and the contact end 10 after the insulating material 6 has been applied. Then, after the solvent has been removed from paste 3 by means of a drying process, the impregnation and hardening take place. The band 7 shrinks at the temperature required for hardening, presses the sealing media at the contact end outlet firmly together and pulls the contact end 10 firmly against a coil end or arm portion of the coil.

The drying process for removing the solvent from the paste 3 usually takes place in the course of the drying process required for impregnating the remainder of the coil and therefore without any additional expenditures or loss of time. In a specific example of a coil waterproofed according to the invention the above mentioned lengths L, L,, L, and L, measured in centimeters: L= 90, L, 40, L 35 and L 10. In order to insulate this coil to with stand a normal ac. voltage of 4.5 kilovolts, the material 2 was wound with an overlap of one half over the length L, with a total number of three layers, and the material 5' was wound with an overlap of one half over the length L with a total number of two layers. The band 7 usually is a woven polyester tape which shrinks at the hardening temperature of the impregnating resin of 150C.

The method according to the present invention can in principle also be used for sealing the portions of the coil disposed in the area of the lamination packet of an electrical machine. However in the lamination packet or more precisely in the notches of the packet a waterproof seal is generally obtained by carefully wrapping the coil because in the notches the coils are straight and therefore do not have any cavities.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. In a method of waterproofing electrical coils, particularly for use in electrical machines, in which the coils are wrapped with a substantially unimpregnated insulating material, are then inserted, except for the coil ends or arm portions and the contact end outlets, into notches of a lamination packet of themachines, and then have the insulating material impregnated by saturation with a resinous material, the improvement comprising the steps of: preparing a thick but still spreadable paste consisting substantially of a powdered coil before wrapping the coil with the substantially unimpregnated insulating material but after the application of said paste.

3. A method as defined in claim 1, wherein the removal of said solvent takes place before the coil is inserted into the notches.

4. A method as defined in claim 1, wherein the removalof said solvent takes place after the coil is inserted into the notches.

5. A method as defined in claim 1, further comprising the step of inserting an angular strip of insulating material into the cavities at the contact end outlets which are between the contact ends and the remainder of the coil before the cavities are filled with said paste.-

6. A method as defined in claim 5 further comprising the step of covering said angular strip with said paste on at least one side thereof.

I UNITED STATES PATENT OFFICE (TERTTFTCATE OF CORRECTION Patent N 3,840 ,416 Dated October 8th. 1974 Inventor($) Schinde'lme-i =0? n+- 21 that error appears in the above-identified patent reby corrected as shown below:

line 13, change "7113167" to It is certified and that said Letters Patent are he In the heading ofthe patent, v 2ll6603-. I

"intially" to -initially--;

Column 4, line 1, change proof to --waterproof--.

line 47,, change "water- Signe'dand sealed this 7th day of January 1975.

(SEAL) Attest I I McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer II Commissioner of Patents USCOMM-DC GUSTO-P69 U.5. GOVERNMENT PRINTING OFFICE lll l 0-860-834.

FORM P0-1050 (10-69) UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Dated October 8th. 1974 Patent No. 3,840,416

Schindp'lmpi cor pi- 31 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Inventor(s) In the heading of the patent, line 13, change "7113167" to line 1, change Column 4, "intially" to -initially-;

' line 47 change "water-proof" t o -waterproof.

Signed and sealed this 7th day of January 1975.

'(SEAL) Attest:, I McCOY M. GIBSON JR. c. MARSHALL DANN Commissioner of Patents Attesting Officer USCOMMDC 60876-PB9 R U.S. GOVERNMENT PRINTING OFFICE Ill! osu-su.

F ORM PO-I 050 (10-59) 

1. In a method of waterproofing electrical coils, particularly for use in electrical machines, in which the coils are wrapped with a substantially unimpregnated insulating material, are then inserted, except for the coil ends or arm portions and the contact end outlets, into notches of a lamination packet of the machines, and then have the insulating material impregnated by saturation with a resinous material, the improvement comprising the steps of: preparing a thick but still spreadable paste consisting substantially of a powdered filler material and a volatile solvent; prior to wrapping, completely filling all of the cavities or voids in at least the coil ends or arm portions and the contact end outlets of the coil by applying a sufficient quantity of said spreadable paste thereto; and removing said solvent from said paste by a drying treatment after wrapping but before impregnating the coil.
 2. A method as defined in claim 1, further comprising the step of wrapping a band around at least the coil ends or arm portions and the contact end outlets of the coil before wrapping the coil with the substantially unimpregnated insulating material but after the application of said paste.
 3. A method as defined in claim 1, wherein the removal of said solvent takes place before the coil is inserted into the notches.
 4. A method as defined in claim 1, wherein the removal of said solvent takes place after the coil is inserted into the notches.
 5. A method as defined in claim 1, further comprising the step of inserting an angular strip of insulating material into the cavities at the contact end outlets which are between the contact ends and the remainder of the coil before the cavities are filled with said paste.
 6. A method as defined in claim 5 further comprising the step of covering said angular strip with said paste on at least one side thereof. 